NitroImg is the only WordPress image optimizer that works page by page instead of through the media library. Select specific posts or pages, see exactly which images will be converted and what it will cost, then convert — all from the posts list. One credit per image, non-destructive, with one-click rollback.
This guide covers installation, configuration, the conversion workflow, rollback, auto-convert, srcset handling, and credit pricing.
nitroimg.zip and click Install NowAlternatively, unzip the file and upload the nitroimg/ folder to /wp-content/plugins/ via FTP, then activate from the Plugins screen.
All settings are under Settings → NitroImg. The page is organized into two cards: License and Conversion.
Enter your NitroShock license key to activate image conversion credits. The key is stored securely and masked after saving. A green "Active" indicator appears when a valid key is saved. You can get a key by signing up at nitroshock.ai.
Controls the output quality of converted WebP images. Accepts values from 1 to 100. The default of 82 is optimal for most images — it produces significant file size savings while maintaining visual fidelity that's indistinguishable from the original in normal viewing conditions.
Lower values (60–75) produce smaller files with visible compression artifacts. Higher values (90–100) produce larger files with minimal quality difference from the original. For photography-heavy sites, 85–90 is a reasonable choice. For UI screenshots and graphics with sharp edges, 82 works well.
Images below this file size threshold are excluded from conversion. The default is 10,240 bytes (10 KB). Tiny images like icons, spacers, and 1×1 tracking pixels don't benefit from WebP conversion and aren't worth spending credits on. Set to 0 to disable the threshold and convert everything.
When enabled, every newly uploaded JPEG or PNG image is automatically converted to WebP immediately after upload. This includes all WordPress-generated thumbnail sizes and any custom sizes registered by your theme. Uses 1–3 credits per upload depending on file size. If credits run out or the API is unreachable, the upload proceeds normally — auto-convert never blocks or fails an upload.
NitroImg's workflow is page-based rather than media-library-based. Instead of converting your entire image library (which wastes credits on images that may never be displayed), you convert only the images actually used on specific posts and pages.
Select multiple posts or pages using the checkboxes in the list table, then choose Convert Images from the Bulk Actions dropdown. The modal scans all selected pages together and shows the combined image count and credit estimate. This is efficient for converting an entire section of your site at once.
The scanner finds images from all of these sources on each page:
Images that are already converted to WebP, or that fall below the minimum size threshold, are automatically excluded from the conversion count.
When you click Convert, NitroImg processes each image through the following steps:
The URL replacement is a clean, direct swap — no .htaccess rewrite rules, no <picture> tag wrappers, no JavaScript lazy-loading. The WebP URL replaces the original URL in post_content and the srcset filter handles responsive image delivery.
NitroImg hooks into WordPress's wp_calculate_image_srcset filter so converted attachments automatically serve WebP URLs in all responsive image contexts. This means:
srcset attributes use WebP URLs for all converted sizesNo configuration needed. The filter has zero overhead for unconverted images — it only activates for attachments that have conversion metadata.
NitroImg is fully non-destructive. Original JPEG/PNG files are never deleted. You can revert any converted image back to its original format:
After rollback, the image serves in its original format exactly as it did before conversion. No credits are refunded for rolled-back images.
NitroImg adds several features to the Posts and Pages list screens:
A Convert Images link appears in the row actions (hover menu) for every post and page. Click it to open the conversion modal for that specific page.
The Convert Images option in the Bulk Actions dropdown lets you process multiple pages at once. Select the posts you want, choose the action, and the modal scans all of them together.
A WebP column shows the conversion status for each post — how many images are converted versus how many are present on the page. This gives you a quick visual overview of which pages have been optimized.
Credits are charged per original image, not per thumbnail size. A single image with 7 WordPress-generated sizes still costs just 1 credit.
The conversion modal always shows the exact credit cost before you commit. If you don't have enough credits, a warning appears with a link to purchase more at nitroshock.ai/pricing.
Your first image conversion is completely free — no credit card required. This lets you test the quality and workflow before purchasing credits.
NitroImg automatically detects WooCommerce product gallery images in addition to featured images and content images. When you click Convert Images on a product page, the scanner finds all gallery images attached to that product. Conversion and rollback work identically to regular posts.
If you deactivate NitroImg, converted WebP files remain on disk and the updated URLs in your post content continue to work — your images keep serving as WebP. The srcset filter stops running, so responsive images fall back to WordPress's default behavior (which still serves the WebP URLs stored in post content).
If you delete the plugin entirely, all NitroImg metadata is removed from the database, but converted WebP files are preserved on disk. To fully revert to original images before deleting, use the rollback feature on each post first.
tested fallback in updater to prevent "not tested with your version" warningOne credit for images up to 2 MB, two credits for 2–10 MB, three credits for images over 10 MB. Credits are charged per original image — not per thumbnail size. An image with 7 WordPress sizes costs 1 credit.
Yes. Your first image conversion is completely free — no credit card required.
No. NitroImg is non-destructive. Original JPEG/PNG files remain on disk. WebP versions are saved alongside them. You can roll back any image at any time.
Yes. NitroImg scans featured images, in-content images, and WooCommerce product gallery images.
Yes. NitroImg filters WordPress's srcset output at render time so all thumbnail sizes serve the WebP version automatically. No configuration needed.
The conversion stops at the current image and reports the partial result. Images already converted stay converted. You can purchase more credits and resume by clicking Convert Images again — already-converted images are skipped.
Yes. NitroImg scans the saved post_content for image references, which works with Gutenberg, Classic Editor, Oxygen Builder, Elementor, and any builder that stores content in the standard WordPress content field.
Updates are delivered directly from NitroShock. You'll see update notifications in your WordPress dashboard just like any other plugin. Click "update now" to install.
NitroImg sends images to the NitroShock API for conversion. No visitor data, cookies, or tracking is involved. The API processes images and returns the WebP versions — no image data is retained on NitroShock servers after conversion completes.
Most WordPress sites have hundreds or thousands of images in the media library, but only a fraction are actively displayed on published pages. Page-based conversion lets you optimize only what matters — the images visitors actually see — without wasting credits on unused uploads, draft content, or orphaned media.